1. Field of the Invention
This invention relates to an image recording apparatus, and more specifically to an image recording apparatus which can use a recording sheet efficiently.
2. Description of the Related Art
Known image recording apparatuses, such as a copier, are used in combination with a recirculating document feeder (hereinafter referred to as "RDF"). In such a known image recording apparatus, originals in a stacking tray are separated one by one from the bottom of an original bundle, and a separated original is fed to an exposure position for exposing. After the completion of an exposure operation, the separated original is returned to the tray at the top of the original bundle.
Referring to FIG. 6A through 6C, a general sheet feed sequence system will be described in detail.
In FIG. 6A, an original S3 from the bottom of an original bundle S set in a RDF, such as three sheets of originals, is transported to an original platen 101. Then, a recording material P (hereinafter referred as "copying sheet") is conducted to a registration roller 159 by a feed roller 207 at a time when the original S3 arrives at a predetermined position as shown in FIG. 6B. When the copying sheet P arrives at the registration roller 159, a scanning operation of the original S3 by a illumination lamp 103 is started as shown in FIG. 6C. The registration roller 159 starts to feed the copying sheet toward photosensitive drum 131 at a time when the illumination lamp 103 passes through an image tip sensor 117, so as to record an image on the copying sheet P.
Thus, in a general sheet feed sequence system, the steps of exchanging originals, stoping the new original on the original platen, feeding a copying sheet from a cassette, waiting for the copying sheet to arrive at the registration roller, and starting a scanning operation, are all performed sequentially. No step starts until the previous step is complete.
In the interests of improving copying speed, a previously-fed sheet sequence system has been proposed.
In the previously-fed sheet sequence system, the steps of exchanging originals and stoping the new original on the original platen are performed at the same time as the steps of feeding a copying sheet from a cassette and waiting for the copying sheet to arrive at the registration roller. After all of these steps are completed, the scanning operation is started.
Such a sequence is shown in FIGS. 7A through 7C. In FIG. 7A, the scanning operation of the original S3 by the illumination lamp 103 is started. The registration roller 159 starts to feed the copying sheet to photosensitive drum 131 at a time when the illumination lamp 103 passes through the image tip sensor 117, so as to record an image on the copying sheet P.
In FIG. 7B, the illumination lamp 103 has returned to its initial position upon completion of the scanning operation. The next copying sheet P then starts to be fed by the feed roller 207 at the same time as the next original S2 starts to be transported to the original platen 101 and the transport of the original S3 is started.
The copying sheet P is set to the registration roller 159 before the original S2 is set on the original platen 101 as shown in FIG. 7C. The scanning operation is started at the same time as the original S2 is set on the original platen 101.
According to the previously-fed sheet sequence system, the copying sheet can be fed from a cassette to the registration roller 159 during the setting of an original on the original platen 101. Accordingly, the copying speed is improved as compared with the general sheet feed sequence system.
However, in the above described known image recording apparatus, when an original jamming occurs in the RDF during an exchange of originals, the copying sheet that corresponds to the jammed original has already been fed. Since the copying sheet cannot be returned to the cassette, the copying sheet cannot be used after the jam is cleared and is unavoidably discharged out of the apparatus as a plain sheet without being used.
Accordingly, the known image recording apparatus suffers from a problem in that one copying sheet is consumed whenever an original jamming occurs.
The known image recording apparatus also suffers from a problem in that the count of copied sheets is erroneously increased whenever the unused sheet is discharged.